Renewable indicating fuse plug



June 6, 1939 H. M. MUNCHERYAN 2,161,079

RENEWABLE INDICATING FUSE PLUG Filed March 215, 1956 Patented June 6, 1939 UNITED STATES PATENT OFFICE RENEWABLE INDICATING FUSE PLUG:`

Application March 23, 1936, Serial No. 70,262

1 Claim.

My invention relates generally to fuse plugs, and more particularly to a plug having readily insertable and removable means for indicating the condition of the fuse within said plug, that is,

5 whether or not the fuse has blown or been ruptured as a result of overloading in the circuit in which the plug is located, and the principal object of my invention is to provide a relatively simple,

. practical and inexpensive fuse plug adaptable for 1 use in standard sockets, and said plug having a chamber adapted to receive a fuse, which latter may be easily and conveniently inserted in the plug or removed therefrom in the event that the fuse is blown, thus enabling a blown fuse to be u' easily and quickly removed and replaced by an unblown fuse, and said fuse having associated therewith, an indicating element that is destroyed when the fuse is blown, thus providing simple and efficient means for indicating the condition of the plug and its fuse, and which result is especially desirable where a number of fuse plug receiving sockets are mounted in a fuse box or on a panel.

Further objects of my invention are to generally improve upon and simplify the construction of the existing forms of indicating fuse plugs, and further to provide a plug having a chamber adapted to receive a fuse, with the terminal portions of a pair of spaced contacts arranged within said chamber, for engagement with the inserted fuse, and the terminal portions of said contacts being constructed so as to function as springs to exert yielding pressure on the inserted fuse, and thereby effectively retain the same in position within the plug.

With the foregoing and other objects in view, my invention consists in certain novel features of construction and arrangements of parts that will be hereinafter more fully described and claimed and illustrated in the accompanying drawing in which:

Fig. 1 is a vertical section taken through the center of a renewable indicating fuse plug constructed in accordance with my invention.

v Fig. 2 is a vertical section taken through the center of a modified form of the plug.

Fig. 3 is a vertical section taken through the center of a further modied form of the plug.

Fig. 4 is a vertical section taken through the I'center of a further modified form of plug.

Fig. 5 is a plan view of the forms of plugs illustrated in Figs. 1 to 3 inclusive.

Fig. 6 is a plan view of the form of plug illustrated in Fig. 4.

6l- Fig. 'I is a longitudinal vertical section taken (Cl. 20G-130) through the center of a renewable indicating fuse that is utilized in my improved plug.

Fig. 8 is an horizontal view taken on the line 8-8 of Fig. 7.

Fig. 9 is a longitudinal section similar to Fig. 71 5 and showing a modified form of the renewable indicating fuse.

Fig. 10 is a detail View of the central portion of a modified form of the indicating fuse.

Referring by numerals to the accompanying 10 drawing, and particularly to the form of plug illustrated in Fig. 1, I0 designates a short tubular member that forms the upper or outer portion of the body of the plug, said body member being formed of porcelain, glass, ber, or other suitable insulating material, and formed in the outer or upper portion of said body, is a chamber I I, open at one end on the side of the body in order to receive one of the renewable indicating fuses.

The chamber within the tubular body I0 functions as an expansion chamber for the gases that are developed when the fuse positioned in the plug is blown or ruptured by an overload of current, and the upper portion of this expansion chamber is in direct communication with the fuse-receiving chamber I I.

Applied to the upper end of the body I0, is a disc I2, of suitable insulation that is secured to the body in any suitable manner, preferably by t means of screws I3, and formed in the center of o this disc, is an aperture I4 that communicates with the central portion of the fuse receiving chamber II.

A sheath or shell I5 of thin sheet metal is applied to the lower portion of body I0, and said shell has a thread pressed therein, in order that the plug may be screwed into the conventional socket.

Applied to the lower end of body I0, is a short conical member I6 of suitable insulating ma- 4U terial, and the lower portion of shell I5 is extended beneath a shoulder that is formed on the upper portion of said member, in order to secure the same to the body member I0. Positioned in the center of member I6 is a metal contact I'I, that is adapted to engage the center contact of the .ocket into which the plug is screwed.

Arranged on the inner face of body I0, is a metal strip I8 that functions as a conductor, the same being secured to body I0 in any suitable manner, preferably by means of a screw or rivet I9, and the lower portion of this strip extends downwardly into member I6 and its lower end is electrically connected to contact I1.

A portion of this strip I8 extends beyond the 55 upper end of body I0, and said portion is bent to form a short horizontally disposed portion 2U that is positioned in one end of the fuse receiving chamber II, and the end of the strip beyond this portion 2U is bent downwardly and terminates in arecess 2|, that is formed in the end of body I0. The portion 20 is spaced apart from the adjacent end of body I9, to function as a spring to exert yielding pressure against the inserted fuse to hold the same rmly in the plug.

Located on the opposite side of body IG from conductor I8, is a short conductor strip 22 of metal, the lower end portion of which extends through an opening 23, that is formed through the wall of body I9, and this end is electrically connected to shell I5. The upper portion of member 22 is bent so as to overlie the corresponding upper edge of the wall oi body I9, in the end of the chamber I l opposite the end in which member 20 is formed, thus forming a short horizontally disposed arm 24 that functions as a spring to exert yielding pressure against the end of the inserted fuse.

The form of plug illustrated in Fig. 2 comprising a one-piece body 25 formed of suitable insulating material, in the upper portion of which is formed a diametrically disposed chamber 2G open at one end for the reception or the fuse, and formed in said body below said chamber 26 is an expansion chamber 2'I that tapers toward its lower end. Expansion chamber 2l is in direct communication with the fuse-receiving chamber 26.

Removably positioned on top of the plug body, and retained thereon by means of screws, or the like, is a cover plate 28 provided in its central portion with an aperture 29. Positioned on the external surface of body 25, is a shell 39 preferably formed of sheet metal in which is pressed a thread, in order that the plug may be screwed into a socket, and seated in the lower end of body It), is a metal contact 3l that is adapted to engage the center contact of the socket into which the plug is screwed.

A metal conductor 32 extends lengthwise through the body 25 of the plug, and the lower end of this conductor is electrically connected to contact 3|. The upper portion of this strip 32 is extended into the fuse receiving chamber 2G adjacent its open end, and said portion is bent to form a short horizontally disposed member 33 that functions as a spring to exert pressure against the inserted fuse.

The free end of this portion 33 is bent downwardly into a recess 34 that is formed in the upper lace of body 25. On the opposite side of body 25 from conductor 32, is a short conductor 35 that extends through an opening 36 that is formed in said body, and the lower end of said conductor is connected to shell 30. The upper portion of conductor 35 projects into the end of 'the fuse chamber 26 opposite the open end thereof, and this portion of said conductor is bent into a horizontal plane, as designated by 38, to provide a spring that yieldingly engages the end of the inserted.

fuse.

The form of plug illustrated in Fig. 3 is practically the same as that illustrated in Fig. 2, with the exception that the conductor 32, instead of extending through the greater portion of the body 25, is extended downwardly from the fuse chamber 26, through the tapered chamber 2 on the inner face thereof, and the lower portion of said conductor is electrically connected to the upper end of center contact 3|, instead of to the lower end, as is the case in the construction illustrated in Fig. 2.

The renewable indicating fuse that is utilized with the forms of plugs illustrated in Figs. 1, 2 and 3, is illustrated in Figs. '7, 8 and 9, and each fuse comprises a body or ller member 39 formed of suitable insulating material, for instance, ber, hard rubber, Bakelite, or the like, and formed in the center of said member is an aperture 49. The forward end of this member 39 is rounded or pointed to facilitate its entry into the chambers of the upper portions of the plugs, and formed in the under side of the rear end of said member is a transversely disposed notch 4I that may be engaged by the fingernail, when a blown fuse is removed from the plug.

Applied to the under side of member 39, and extending across opening 49 is a use 42, and positioned on top of member 39 and extending across the aperture 49 therein, is a strip 43 of thin material such as paper, Celluloid, or the like. In the event that paper strips are utilized the same are preferably treated with a substance that renders the paper highly inflammable, so that it will burn and be destroyed when the fuse that is located on the opposite side ol member 39 blows, or is ruptured, as a result ol overload of current. That portion ofthe indicating strip 43 of paper, Celluloid, or the like, that passes across the opening 49 is preferably pressed downward into said opening, so that the intermediate portion of said strip rests directly upon that portion oi the fuse that blows or ruptures, and thus the ignition and destruction of the indicating member by the fuse when the same is blown, is insured.

Printed on the upper surface of that portion of the indicating element i3 that passes across the opening 49 are letters or characters that indicate that the fuse is unblown, for instance, the letters O. K. may be utilized so that a person inspecting the fuse plugs and noting that the marked portion of the strip 42 is unblown, will understand that the plug is in good condition and functions properly.

Overlying the indicating strip 43 is a narrow strip 44 of non-combustible transparent material, preferably mica, the width thereof being approximately equal to the width of the filler member 39. To maintain the parts 39, 42, 43 and "54 in assembled relation and provide a practically one piece fuse unit, a band i5 oi thin metal is pressed around the rear ends of the parts just mentioned, and a rounded or pointed cap 46 of thin sheet metal is pressed on the forward portions of the fuse elements.

The fuse thus constructed is inserted in the chamber at the top of the plug, for instance, chamber I I of the plug illustrated in Fig. 1, or the chamber 26 of the plugs illustrated in Figs. 2 and 3, and the inserted member is held in position within the chamber by the pressure exerted by the springs 20 and 24, or the springs 33 and 38. Thus it will be understood that the springs that press against the inserted fuse to hold the same in the plug also function as electrical contacts, for when the fuse is properly inserted in the plug, the springs bear directly upon the metal band 45 and cap 45, and which latter parts are directly in contact with the ends of the fuse 42.

In the modified construction of the fuse illustrated in Fig. 9, the strip oi" paper or Celluloid 43 that bears the indicating letters or characters extends straight across the opening 48 in member 39, and the intermediate portion of fuse 42 is bent upwardly, so that its intermediate portion contacts with the underside of the central portion of said strip of paper, or Celluloid.

As a result of the proximity of the marked portion of the strip of paper or Celluloid, to that portion of the fuse that is destroyed when the fuse blows, the greater portion of the strip of paper or Celluloid that occupies or passes across opening 40, will be burned out and destroyed upon the blowing of the fuse.

In the modified construction illustrated in Fig. 4, the body 41 of a plug formed of suitable insulating material, is provided with an expansion chamber 48, and formed ln the top of the body of this plug and communicating with the upper end of chamber 48, is a transversely disposed fuse receiving chamber 49 closed at both ends. Applied to the exterior of the body of the plug is a metal shell 50 in which is pressed a thread, in order that the plug may be screwed into a socket, and located in the lower end of the plug is a contact 5I. A conductor 52 extends lengthwise of the chamber 48 immediately adjacent the surface of the wall surrounding said chamber, and the lower end of this conductor is electrically connected to contact 5|. The upper portion of this conductor is extended horizontally within one end of the chamber 49, to provide a fuse engaging spring and vcontact 53.

Arranged in the opposite end of the chamber 49, is a combined fuse engaging contact and spring 54, that is formed on the upper end of a conductor 55, the lower end of the latter being electrically connected to shell 50. Detachably secured to the upper end of this form of plug, is a cover plate 56 having a centrally arranged opening 51, through which the central portion of the inserted fuse is readily visible.

Where this form of plug is utilized, the cover plate 46 must be removed in order to permit a fuse to be positioned within chamber 49, and said cover must also be removed when a blown fuse is removed from the chamber. When a fuse is properly positioned within chamber 49, the metal band 45 and metal cap 46 on the ends of the fuse, and which are electrically connected to the fuse 42, are in direct contact with the springs 53 and 64, and which latter engage the ends of the fuse with pressure so as to firmly hold the same in proper position.

In the modified form of fuse illustrated in Fig. 10, the relatively narrow central portion of the fuse body that is destroyed when the fuse blows, has formed therein, the letters O. K., or other characters to show that the fuse is in condition to function properly.

In the event that the fuse blows as a result of overload, the portion bearing the indicating characters is destroyed, and such condition may be readily noted when the fuse is inspected, inasmuch as the narrow portion of the fuse is positioned immediately below the opening in the top or cover plate of the plug.

Thus it will be seen that I have provided a renewable indicating fuse plug that is relatively simple in construction, inexpensive of manufacture and very effective in performing the functions for which it is intended.

It will be noted that in all forms of the plug the expansion chamber which is provided to accommodate the expansion of gases produced when the carried fuse is blown or ruptured, is in direct communication with the chamber formed in the top or head of the plug, and which receives the fuse.

It will be understood that minor changes ir. the size, form and construction of the various parts of my improved renewable indicating fuse plug may be made and substituted for those herein shown and described, without departing from the spirit of my invention, the scope of which is set forth in the appended claim.

I claim as my invention:

In a renewable fuse plug having an opening therein and a xed contact on either side of said opening; a renewable fuse unit extending across said opening and bridging said contacts, said unit comprising an electric current conducting fusible element, a combustible body overlying said element and in contact therewith, a sheet of fireproof transparent material overlying said body and closing said opening, and means connecting said element, body and sheet together to form said unit.

HRAND M. MUNCHERYAN, 

